1. Field of the Invention
The present invention relates to a fuel injection control device for an internal combustion engine.
2. Description of Related Art
Japanese Unexamined Patent Publication No. 2-169834 discloses an internal combustion engine having a spark plug and a fuel injector for injecting fuel directly into the cylinder. In this disclosure, under a low engine load, a fuel injection only during a compression stroke is carried out, i.e., the fuel injector injects all of an amount of fuel to be injected during approximately the latter half of the compression stroke, and under a middle or high engine load, a divided fuel injection is carried out, i.e., during the fuel injection a part of an amount of fuel to be injected is injected during an intake stroke, and a remaining part of the amount of fuel to be injected is injected during a compression stroke.
In this engine, however, even though an engine load is constant, if a control pattern of a fuel injection (e.g., a fuel injection only during a compression stroke or a divided fuel injection) is changed, the engine torque is changed, for example, the engine torque when a fuel injection is made only during the compression stroke is different from the engine torque when a divided fuel injection is made.
Accordingly, when the control pattern of the fuel injection is successively changed, for example, from the fuel injection only during the compression stroke to the divided fuel injection over all of the cylinders, a torque difference between the fuel injection only during the compression stroke and the divided fuel injection, corresponding to each cylinder, is added over all of the cylinders, and thus a large average torque difference occurs, and as a result, a problem arises in that a large torque shock occurs.